Flap valve sealing arrangement

ABSTRACT

Flap valves include a valve housing and a flap disc in a flow channel of the valve housing. The flap disc can be pivoted between an open position and a closed position. The flow channel on its outer circumference includes a sealing lip arrangement, which has two elastic sealing lips arranged at a distance from each other in the direction of flow. With the valve disc in the closed position, the sealing lips bear under elastic prestress against the sealing surface of the valve disc to form a seal and thereby form an annular cavity surrounding the sealing surface of the valve disc. Further, with the flap disc in the closed position, the passage of fluid from the high-pressure side in the flow channel to the low-pressure side of the flow channel prevented due to the cross-sectional areas of the two sealing lips of the sealing lip arrangement being inclined or bent towards the inside of the annular cavity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT/EP2020/068397 filed Jun. 30,2020, the contents of which are hereby incorporated by reference in theentirety and for all purposes.

FILED OF THE INVENTION

The present technology relates to flap valves, also known in theEnglish-speaking world as “butterfly valves”.

BACKGROUND OF THE INVENTION

A flap valve comprises a valve body defining a flow channel for the flowof a liquid or gaseous fluid and a flap valve disc mounted on the valvebody and pivoting about a pivot axis. The dimensions and shape of theflap valve disc correspond to the cross-section of the flow channel. Thevalve disc can be swiveled about a swivel axis between a closed positionand an open position. In the closed position, the valve disc rests witha sealing surface on the outer circumference of the flap valve discagainst an annular sealing lip assembly located on the innercircumference of the flow channel and in the closed position blocks theflow of liquid or gaseous fluid through the flow channel. In the openposition, the fluid flows around the flap valve disc and can passthrough the flow channel.

Publication DE 43 43 562 A1 describes a flap valve including: a valvebody designed for installation between two sections of a pipeline andprovided with a flow channel for the flow of a fluid, a valve discarranged in the flow channel and pivotable between a closed position andan open position and mounted on the valve body, this valve disc shuttingoff the flow of the fluid in the closed position and opening the passageof the fluid in the open position, and an annular sealing liparrangement which is fastened to the inner circumference of the flowchannel, surrounds the flow channel and has two annular sealing lipswhich consist of elastic material. The two annular sealing lips arearranged at a distance from one another in the direction of flow, bearwith their inner sealing edges under elastic prestress against a sealingsurface located on the outer circumference of the valve disc when thevalve disc is in the closed position, thereby forming an annular cavitysurrounding the sealing surface of the valve disc.

Sealing lip arrangements with elastically yielding sealing lips have theadvantage over non-elastic seals that the drive torques required to openand close the valve disc remain relatively low. Similarly constructedflap valves are described in DE 28 29 066 C2, EP 0 412 229 B1 and DE 19515 014 A1. In the flap valves described in these publications, thecross-sectional areas of the two sealing lips of the sealing liparrangement are inclined or bent outwards in relation to an annularcavity defined between the two sealing lips, i.e. against the directionof flow of the fluid, for example as shown in FIG. 5. As a result, thefluid flowing to the flap valve in the direction of the pressure dropfrom the high-pressure side to the low-pressure side attempts, when theflap disc is in the closed position, to press these outwardly inclinedor bent sealing lips back into the annular cavity lying between them,whereby the contact pressure with which the inner sealing edges of thesealing lips are pressed against the sealing surface of the flap discincreases due to the special cross-sectional shape of these sealinglips.

If uncontrollable pressure increases occur on the high-pressure side ofa sealing lip arrangement as shown in FIG. 5, this increase in contactpressure, as explained above, continues until the sealing lip on thehigh-pressure side gives way or is destroyed, so that the fluid entersthe annular cavity between the two sealing lips at high pressure, pushesback the second sealing lip on the low-pressure side in the openingdirection and passes through largely uncontrolled towards thelow-pressure side.

There is therefore a need for a flap valve to prevent uncontrolledpassage of fluid from the high-pressure side to the low-pressure side asdiscussed above.

BRIEF SUMMARY

The present technology relates to a flap valve wherein thecross-sectional areas of the two sealing lips of the sealing liparrangement are inclined and/or bent towards the interior of the annularcavity.

In the flap valve in accordance with the present technology, thepressure increases on the respective high-pressure side of the flapvalve as explained above lead to the sealing lip of the sealing liparrangement on the high-pressure side being pressed down towards theinterior of the annular cavity by the action of pressure. With thisdepressing force being greater than the elastic restoring force of thesealing lip on the high pressure side, the fluid may enter the annularcavity between the two sealing lips slowly and without destroying thesealing lip on the high pressure side. The fluid entering the annularcavity builds up a counter-pressure within the annular cavity whichsupports the sealing lip on the high pressure side from its interiorside, so that the sealing lip on the high pressure side is protectedagainst the uncontrolled passage of fluid or destruction. With thepressure in the annular cavity corresponding to the pressure of thefluid on the high pressure side, the sealing edge of this sealing lip onthe high pressure side contacts with the sealing edge of the sealingsurface of the valve disc with the sealing effect predetermined by theelastic pretension of the sealing lip.

Due to the cross-sectional shape and alignment of the low-pressure sidesealing lip of the sealing lip arrangement, fluid that has penetratedinto the annular cavity cannot leave the annular cavity in the directionof the low-pressure side either, due to the sealing lip on thelow-pressure side increasing its sealing effect when pressurized fromthe annular cavity due to the inclination and/or curvature of thissealing lip directed against the direction of the pressure drop. Thesealing lip on the high-pressure side and thus the entire sealing liparrangement is thus considerably less sensitive to uncontrollablepressure increases that sometimes occur.

In embodiments, in order to be able to easily replace the sealing lipassembly together with the two sealing lips when necessary, the twosealing lips of the sealing lip assembly may be attached to a supportring which is insertable into a matching annular recess on the innercircumference of the flow channel of the valve body. The sealing lips,which may be made of stainless steel, may be welded to the support ring.

In embodiments, the two sealing lips and/or the back-up ring aremanufactured in an additive process from metallic materials withelasticity and hardness adapted to local requirements. This makes itpossible to adapt the sealing lip arrangements to the requirements withregard to their dimensions and their shape and material properties. Inorder to be able to use the annular cavity located between the twosealing lips for improving the sealing effect and/or further functions,in embodiments the annular cavity located between the sealing lips maybe connected to a pressure fluid channel leading out of the valvehousing. This pressure medium channel leading out of the valve body maybe connected to a pressure medium source. This makes it possible toinfluence the pressure prevailing in the annular cavity between thesealing lips and thus the sealing effect of the sealing lips in atargeted manner by pressurizing or reducing the pressure, for exampledepending on the pressure difference across the flap valve.

In embodiments, as an alternative or in addition to the above-mentionedpressure medium source, the pressure medium channel leading out of thevalve housing may be connected to a lockable collecting device forleakages. This is beneficial in removing residual medium from theannular cavity.

In embodiments, as an alternative or in addition to the measuresdiscussed above, the pressure medium duct leading out of the valvehousing may be provided with a supply device for providing a settingand/or hardening sealing agent. Such sealing agents, which may be usedin an emergency, may permanently block the flap valve in the closedposition and subsequently make it necessary to remove the entire sealinglip arrangement. According to the present technology, this emergency useis particularly promising for the flap valve because the sealing agentcan be filled in at particularly high pressure due to the special designand arrangement of the sealing lips.

Embodiments of the present technology relate to methods of usingembodiments of the flap valves as disclosed herein. In embodiments, thepresent technology relates to a method for increasing the sealing effectof a flap valve, in which the pressure medium channel leading out of thevalve housing is connected to a pressure medium source, this methodbeing characterized in that, after the flap disc has reached the closedposition, the annular cavity located between the sealing lips ispressurized by means of the pressure medium source via the pressuremedium channel. In embodiments, the present technology relates to amethod for observing and/or monitoring leaks on a flap valve, in whichthe pressure medium channel leading out of the valve housing isconnected to a collectors device which can be shut off, this methodbeing characterized in that, when the flap disc is in the closedposition, the annular cavity located between the sealing lips isconnected to the collector device via the pressure medium channel and iskept under observation. In embodiments, the present technology relatesto a method for the emergency shut-off of a flap valve, in which thepressure medium channel leading out of the valve housing is connected toa supply for a setting and/or hardenable sealing agent, this methodbeing characterized in that, when the flap disc is in the closedposition, the annular cavity located between the sealing lips is actedupon by the setting and/or hardenable sealing agent via the pressuremedium channel, the filling pressure of the sealing agent being greaterthan the pressure of the fluid flowing through the flap valve at theflap valve.

In embodiments, the sealing lip arrangement according to the presenttechnology, as disclosed above, may be coupled to the outercircumference of the valve disc additionally or alternatively to thevalve body.

In embodiments, the present technology relates to a flap valve includinga valve body designed for installation between two sections of apipeline and provided with a flow channel for the flow of a fluid. Theflap valve further may comprise a valve disc arranged in the flowchannel and pivotable between a closed position and an open position andmounted on the valve housing, this valve disc shutting off the flow ofthe fluid in the closed position and opening the passage of the fluid inthe open position. The flap valve further may comprise an annularsealing surface which is arranged on the inner circumference of the flowchannel of the valve housing and against which, when the valve disc isin the closed position, a sealing lip arrangement arranged on the outercircumference of the valve disc rests, which sealing lip arrangement hastwo elastic sealing lips which are arranged at a distance from oneanother in the direction of flow and which, when the valve disc isclosed, rest with their outer sealing edges under elastic prestressagainst the sealing surface of the housing, thereby forming an annularcavity surrounding the valve disc. This flap valve may be characterizedby the cross-sectional surfaces of the two sealing lips of the sealinglip arrangement being inclined and/or curved towards the interior of theannular cavity.

In embodiments, the two sealing lips of the sealing lip arrangement maybe attached to a support ring, which in this case can be inserted into asuitable annular recess on the outer circumference of the valve disc sothat the sealing lip arrangement is replaceable.

In embodiments, in order to achieve sealing effects the sealing lipsand/or the support ring are manufactured in an additive process frommetallic materials with elasticity and hardness adapted to localrequirements.

In the following, the invention is further explained by means of adetailed description in connection with the attached drawings, in whichthe same reference signs indicate identical structural elements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-section of a flap valve in the closed position witha sealing arrangement according to embodiments of the presenttechnology.

FIG. 2 shows an enlarged detail A from FIG. 1.

FIG. 3 shows a cross-section of a first design of the back-up ring andthe sealing lips attached thereto according to embodiments of thepresent technology.

FIG. 4 shows a cross-section of a second design of the back-up ring withthe sealing lips attached thereto according to embodiments of thepresent technology.

FIG. 5 shows schematically the pressurization of a double liparrangement according to the state of the art.

FIG. 6 shows schematically the pressurization of a double liparrangement according to embodiments of the present technology.

FIG. 7 schematically shows the arrangement of a flap valve according toembodiments of the present technology in a pipeline together with theconnectable additional units.

FIG. 8 shows a flap valve similar to FIG. 2, in which the sealing liparrangement is located on the outer circumference of the valve discaccording to embodiments of the present technology.

DETAILED DESCRIPTION

For the purpose of explanation, some specific details are given in thefollowing description to allow a thorough understanding of the manyaspects and embodiments of the technology disclosed herein. Differentaspects and embodiments of the technology can be practicedindependently. In some cases, known structures and devices are onlyshown schematically in order to avoid obscuring the underlyingprinciples, aspects and embodiments of the invention. Identicalreference signs and designations in the different figures indicateidentical elements.

FIG. 1 shows an embodiment of a flap valve according to the presenttechnology, which is designated in its entirety by the reference sign100. The flap valve 100 has a valve body 1 surrounding a flow channel200 through which a liquid and/or gaseous fluid can flow.

Valve body 1 is also provided at both ends with connecting flanges 2 and3, which can be used to connect it to a pipeline 300 (see FIG. 7). Inthis way the flap valve 100 is connected to the pipeline 300 andcontrols the flow of gaseous or liquid fluid through this pipeline 300.

In the flow channel 200 of the valve body 1 there is a circular disc 4,whose dimensions and shape are adapted to the cross-section of the flowchannel 200. This valve disc 4 is attached to a swivel axis 5 runningparallel to a plane of extension of the valve disc 4 and supported inthe valve body 1 and can be swiveled between an open position and aclosed position by means of this swivel axis 5. In the open position,the plane of the flap disc 4 runs essentially parallel to the axis ofthe flow channel 200, so that the fluid flowing to the flap valve 100can pass around the flap disc 4 through the flow channel 200. In theclosed position shown in FIG. 1, the flap disc 4, in contrast, restswith a sealing surface 6 on its outer circumference against an annularsealing lip arrangement 7,8 located on the inner circumference of theflow channel 200 and thus blocks the flow of fluid through the flowchannel 200. In the design example shown in FIG. 1, the sealing surface6 of the flap disc 4 is conical in shape, because the flap disc 4 ismounted here in multiple eccentricity.

As further shown in FIGS. 1 and 2, the annular sealing lip arrangement7,8 has two annular sealing lips 7 and 8. These sealing lips are made ofa resilient material, such as stainless steel or other suitable elasticmaterial, and are fixed to the inner circumference of the flow channel200 of valve body 1, spaced apart in the direction of flow. The twosealing lips 7 and 8 each have an inner sealing edge 7 a and 8 a,respectively, with which they rest under elastic pretension againsttheir sealing surface 6 when the valve disc 4 is in the closed position,and an outer fixing edge 7 b and 8 b, respectively, with which they arefixed to the inner circumference of the flow channel 200 of the valvebody 1. When the valve disc 4 is in the closed position, the two sealinglips 7 and 8 form a closed, annular cavity 9 between them in cooperationwith the sealing surface 6 of the valve disc 4.

The cross-sectional surfaces of the two sealing lips 7 and 8 of thesealing lip arrangement 7,8 are inclined and/or bent towards theinterior of this annular cavity 9, as can be seen particularly well inFIGS. 3 and 4. This particular inclination and/or bending of thesesealing lips 7 and 8 has surprisingly beneficial effects on the sealingbehavior, as will be explained below.

There are various possibilities for an easy to handle, replaceableattachment of the sealing lips 7 and 8 to the inner circumference of thepassage channel 200 of valve body 1.

In embodiments, for example as shown in FIG. 2, an annular recess 10 isprovided on the inner circumference of the passage channel 200, intowhich a support ring 11 for the sealing lips 7 and 8 can be inserted. Inthis case the sealing lips 7 and 8 are clamped in the area of theirouter fixing edges 7 b and 8 b in the annular recess 10 with the aid ofthis support ring 11.

In embodiments, for example as shown in FIG. 3, the two stainless steelsealing lips 7 and 8 may be welded to the support ring 11 in the area oftheir fixing edges 7 b and 8 b. In embodiments, stainless materials,other than stainless steel, may also be used.

In embodiments, for example as shown in FIG. 4, the sealing lips 7 and 8and/or the back-up ring 11 are manufactured in an additive process frommetallic materials with elasticity and hardness adapted to localrequirements. For example, by appropriate cross-sectional shape andchoice of material, the sealing lips 7 and 8 can be made relativelystiff in the area of their outer fixing edges 7 b and 8 b, relativelyhard in the area of their inner sealing edges 7 a and 8 a and relativelyelastic in the areas in between. When using this additive process,numerous other adaptations to local requirements are envisioned.

The above mentioned, surprisingly advantageous effect of the design ofthe sealing lip arrangement according to the present technology on thesealing behavior is explained in the following by means of a comparisonbetween a sealing lip arrangement known according to the state of theprior art as shown in FIG. 5, and a sealing lip arrangement according tothe technology, as shown in FIG. 6.

For the sealing lip arrangement shown in FIG. 5 in the closed positionaccording to the state of the art (see DE 28 29 066 C2), the valve bodyis marked with a. Two sealing lips b and c are attached to this valvebody at which, in the closed position shown, touch a sealing surface elocated on a valve disc d. As can also be seen from FIG. 5, the twosealing lips b and c are inclined or bent outwards in relation to theannular cavity f between them.

With this sealing lip arrangement known according to the state of theart as shown in FIG. 5, the pressure on the high pressure side HP in thedirection of arrows 12 increases to such an extent that the sealing lipb becomes permeable in the direction of the annular cavity f, i.e. leaksor is destroyed, or a relatively high pressure quickly builds up in theannular cavity f between the two sealing lips b and c, which issufficient to bend the outwardly inclined or bent sealing lip c locatedon the low-pressure side LP in the opening direction, so that the fluidthat has penetrated into the annular cavity g can pass through to thelow-pressure side LP largely unhindered.

With the sealing lip arrangement according to the present technologyshown in FIG. 6, the pressure on the high pressure side HP in thedirection of arrows 12 becomes so great that the sealing lip 7, which isunder elastic prestress, becomes permeable in the direction of theannular cavity 9, the fluid which penetrates into the annular cavity 9cannot readily leave this annular cavity and builds up an increasedpressure in the annular cavity 9 which supports both sealing lips 7 and8 in the closing/sealing direction. This supporting effect is indicatedin FIG. 6 by arrows 13. With the supporting pressure in the annularcavity increased to correspond to the pressure on the high pressure sideHP, the sealing lip 7 on the high pressure side is again in contact withthe sealing surface 6 of the disc 4 with its original elastic pretensiondue to the supporting pressure from the annular cavity 9. The sealinglip 8 on the low pressure side remains absolutely tightly sealed due toits inclination and/or bending in the direction of the annular cavity 9.

The annular cavity 9, arranged between the two sealing lips 7 and 8, incombination with the shape and arrangement of the sealing lips 7 and 8according to present technology, may be used alone or in combinationwith additional elements of the flap valve in order to further improvethe sealing behavior of the flap valve according to the presenttechnology. For this purpose, as shown in FIGS. 1, 2 and 3, the annularcavity 9 may be connected to a pressure fluid channel 14 leading out ofthe valve body 1.

In embodiments, the pressure medium channel 14 leading out of valve body1 may be used for various purposes, for example as shown in FIG. 7. Asshown there—but only schematically—the pressure medium channel 14leading out of valve body 1 can be connected individually or in anycombination to: a source of pressure medium 15, a lockable collectingdevice 16 for leakages, and/or a feeding device 17 a sealant.

With the aid of the pressure medium source 15, the pressure prevailingin the annular cavity 9 between the sealing lips 7 and 8 may beinfluenced/controlled and thus the sealing effect of these sealing lipsmay be controlled in a targeted manner by applying or reducing pressure,for example as a function of the pressure difference at the flap valve1.

With the leakage collecting device 16 connected to the pressure mediumchannel 14, the sealing effect of the flap valve may be permanentlymonitored. For example, as soon as leaks occur, the leaks can bedetected by the amount of fluid accumulating in the collecting device16.

For a total shut-off of the flap valve, for example in an emergency, theannular cavity 9 between the two sealing lips 7 and 8 can be pressurizedwith a setting and/or hardening sealant via the pressure fluid channel14 with the aid of the sealant supply device 17. Due to the specialdesign and inclination of the sealing lips 7 and 8 according to theinvention, this sealing agent can be introduced into the annular cavity9 at particularly high pressure, so that an absolutely safe and tightemergency seal can be guaranteed.

FIG. 8 shows, in a similar representation to FIG. 2, an arrangement of asealing lip arrangement according to the present technology on the outercircumference of the disc of a flap valve.

In FIG. 8 the body of the flap valve is marked with the reference mark1001 and provided with connecting flanges 1002 and 1003 for connectionof a pipe not shown. In the flow passage 1200 of the valve body 1001there is a flap disc 1004, which can be pivoted about an unshown pivotaxis between a closed position and an open position and is shown in theclosed position in FIG. 8, and which is provided with a sealing liparrangement 1007,1008 on its outer circumference. The sealing lips 1007and 1008 of this sealing lip arrangement, which are made of elasticmaterial, are in contact under elastic prestress with a conical, annularsealing surface 1006, which is located on the inner circumference of theflow channel of the 1200 of the valve body 1001, in the illustratedclosed position of the flap valve.

The two sealing lips 1007 and 1008 of the sealing lip arrangement arealso here arranged at a distance from each other in the flow directionof the flap valve and form an annular cavity 1009 together with theconical sealing surface 1006 of the valve housing 1001 when the flapdisc 1004 is in the closed position. The special feature of this sealinglip arrangement is also here that the cross-sectional surfaces of thetwo sealing lips 1007 and 1008 of this sealing lip arrangement areinclined and/or curved in the direction of the interior of the annularcavity 1009.

The effect of the sealing lip arrangement connected to the flap disc isthe same as for the sealing lip arrangement disclosed above regarding asealing lip arrangement connected to the valve body, as shown in FIGS.1-3.

For easy replacement, the two sealing lips 1007 and 1008 of the flapvalve explained in FIG. 8 may be attached to a support ring 1011, whichcan be inserted into a matching annular recess 1010 on the outercircumference of the flap disc 1004.

In order to be able to better adapt the sealing effect to the localrequirements in terms of shape, elasticity and hardness in this case aswell, the back-up ring 1011 and/or the sealing lips 1007 and 1008 arealso manufactured in an additive process.

In embodiments, with regard to the bearing of the valve disc, differentarrangements may be used, for example different types of valvesincluding: a centric design in which the swivel axis of the disc passesthrough the center of the seal assembly which is centered around theaxis of the flow channel, a single eccentric design, in which the swivelaxis of the disc is axially displaced in the flow direction along theaxis of the flow channel, a double-eccentric design, in which, inaddition to the single-eccentric design, the swivel axis of the valvedisc is displaced perpendicular to the axis of the flow channel, and atriple-eccentric design, in which, in addition to the double-eccentricdesign, the plane of the annular sealing arrangement is no longerperpendicular to the axis of the flow channel. The present technologyrelates to flap valves of all designs.

Different aspects, designs, implementations or features of the describeddesign examples can be used separately in any combination. Inparticular, it should be noted that the various elements of FIGS. 1-4,6and 7 belonging to the concept of the invention can be combined indifferent ways without deviating from the meaning or scope of theinvention.

The indefinite articles “one” or certain articles “the”, “the” or “the”or similar expressions used shall, in the context of the description ofthe invention and in particular in the context of subsequent patentclaims, be interpreted as covering both the singular and the plural,unless such interpretation clearly contradicts the context. The terms“comprising”, “having”, “including” and “contained” shall be interpretedas open terms (i.e. “including but not limited to”) unless otherwiseindicated. The indication of ranges of values is essentially anabbreviation and refers in individual cases to each individual valuefalling within that range, or gradients thereof, unless otherwiseindicated in the description. Each value disclosed in this way istreated as if it were individually mentioned in the description. All thesteps of the procedure described here may be performed in anyappropriate order unless otherwise indicated or the context clearlycontradicts. Examples or indications in exemplary language (e.g. “asis”) are included in the description to better explain embodiments ofthe invention and do not imply any limitation of the scope of protectionof the invention, unless otherwise claimed. No linguistic formulation inthe description should be interpreted as indicating that an unclaimedelement is important for the execution of the invention.

The term “essentially” used in the description refers to the complete oralmost complete extent or degree of an action, characteristic, property,state, structure, object or event. For example, an object that is“substantially” enclosed would mean that the object is either completelyor almost completely enclosed. The exact degree of deviation fromabsolute completeness allowed may depend on the specific context in somecases. In general, however, the closeness to realization will be suchthat the same overall result is achieved as if an absolute and completerealization had been achieved.

The preferred embodiments of the invention described here include thebest way of implementing the invention known to the inventor. Theinvention is open to various modifications and alternativeconstructions. Certain exemplary embodiments of these are shown in thedrawing and have been described in detail above. Variants of thesepreferred embodiments in the sense of the invention may become obviousto the average person reading this description. Inventors expectexperienced skilled persons to be able to use such variants as requiredand to be able to realize the invention in ways other than thosespecifically described here. Accordingly, it is understood that there isno intention to limit the invention to the special form or the disclosedforms. On the contrary, the invention comprises all modifications andequivalents of the subject matter of the invention claimed in theattached claims, as permitted by applicable law. Furthermore, theinvention comprises any combination of the elements described above inall possible variations unless otherwise indicated in the description orunless the context clearly contradicts it. The above description uses aspecific nomenclature for explanatory purposes in order to provide athorough understanding of the embodiments described. However, it isclear to the professional that certain details are not necessary toperform the described embodiments. Thus, the above descriptions ofspecific embodiments are presented for illustrative and descriptivepurposes only. They are not intended to be exhaustive or to limit thedescribed embodiments to those which are individually disclosed. It isobvious to the average expert that many modifications and variations arepossible with respect to the above teachings.

1. A flap valve, comprising: a valve body configured to be coupled between two sections of pipe, wherein the valve body defines a flow channel configured for a fluid to flow through; a flap disc pivotably coupled to the valve body within the flow channel, wherein the flap disc is configured to rotate between a closed position wherein the flap disc blocks a flow of the fluid through the flow channel and an open position wherein the flap disc does not block the flow of the fluid through the flow channel; and a pair of elastic sealing lips coupled to an inner circumference of the flow channel of the valve body within the flow channel, wherein the pair of elastic sealing lips comprise a first sealing lip and a second sealing lip, wherein each of the first and second sealing lips define an inner surface and an outer surface; wherein in the closed position the outer surface under elastic prestress contacts and forms a seal with a sealing surface on an outer periphery of the flap disc, and an annular cavity is defined between the inner surface of the first sealing lip, the inner surface of the second sealing lip, and the sealing surface of the flap disc, and wherein the first sealing lip and the second lip are inclined and/or bent toward each other to define the annular cavity.
 2. The flap valve of claim 1, wherein the first and second sealing lips are each attached to a support ring, wherein the support ring is configured to be inserted into a matching annular recess on the inner circumference of the flow channel of the valve body.
 3. The flap valve of claim 2, wherein in the first and second sealing lips and/or the support ring are produced in an additive process from metallic materials with at least one of elasticity and hardness of different portions of the first and second sealing lips and/or the support ring being different from other portions.
 4. The flap valve of claim 1, wherein the annular cavity defined between the sealing lips is fluidically connected to a pressure medium channel leading out of the valve body.
 5. The flap valve of claim 4, wherein the pressure medium channel leading out of the valve body is connected to a pressure medium source.
 6. The flap valve of claim 4, wherein the pressure medium channel leading out of the valve body is connected to a collecting device configured for detecting leakages.
 7. The flap valve of claim 4, wherein the pressure medium channel leading out of the valve body is connected to a supply configured for delivering a setting and/or curable sealing agent.
 8. A method for operating the flap valve according to claim 5, comprising: positioning the flap disc in the closed positioned; and pressurizing the annular cavity defined between the first and second sealing lips with the pressure medium source in order to increase a sealing force of the outer surfaces against the sealing surface on the outer periphery of the flap disc.
 9. A method for observing and/or monitoring leakages of the flap valve according to claim 6, comprising: positioning the flap disc in the closed positioned; collecting fluid from the annular cavity in the collecting device.
 10. A method for sealing the flap valve according to claim 7, comprising: positioning the flap disc in the closed positioned; filling the annular cavity with the setting and/or hardenable sealing agent through the pressure medium channel.
 11. The flap valve of claim 1, wherein each of the first and second sealing lips define an arcuate profile wherein the outer surfaces are convex and the inner surfaces are concave, wherein the outer convex surfaces of the first sealing lip and the second sealing lip face away from each other, and the inner concave surfaces of the first sealing lip and the second sealing lip face toward each other to define the annular cavity.
 12. A flap valve, comprising: a valve body configured to be coupled between two sections of pipe, wherein the valve body defines a flow channel configured for a fluid to flow through; a flap disc pivotably coupled to the valve body within the flow channel, wherein the flap disc is configured to rotate between a closed position wherein the flap disc blocks a flow of the fluid through the flow channel and an open position wherein the flap disc does not block the flow of the fluid through the flow channel; and a pair of elastic sealing lips coupled to an outer circumference of the flap disc, wherein the pair of elastic sealing lips comprise a first sealing lip and a second sealing lip, wherein each of the first and second sealing lips define an inner surface and an outer surface; wherein in the closed position the outer surface under elastic prestress contacts and forms a seal with a sealing surface on an inner circumference the flow channel of the valve body, and an annular cavity is defined between the inner surface of the first sealing lip, the inner surface of the second sealing lip, and the sealing surface of the flow channel, and wherein the first sealing lip and the second lip are inclined and/or bent toward each other to define the annular cavity.
 13. The flap valve of claim 12, wherein the first and second sealing lips are each attached to a support ring, wherein the support ring is configured to be inserted into a matching annular recess on the outer circumference of the flap disc.
 14. The flap valve of claim 13, wherein in the first and second sealing lips and/or the support ring are produced in an additive process from metallic materials with at least one of elasticity and hardness of different portions of the first and second sealing lips and/or the support ring being different from other portions.
 15. The flap valve of claim 12, wherein the annular cavity defined between the sealing lips is fluidically connected to a pressure medium channel leading out of the valve body. 